TY - JOUR
T1 - Biotin availability regulates expression of the sodium-dependent multivitamin transporter and the rate of biotin uptake in HepG2 cells
AU - Pacheco-Alvarez, Diana
AU - Solórzano-Vargas, R. Sergio
AU - González-Noriega, Alfonso
AU - Michalak, Colette
AU - Zempleni, Janos
AU - León-Del-Río, Alfonso
N1 - Funding Information:
This study was supported by grants of Consejo Nacional de Ciencia y Tecnología (40001-Q) and Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica from Universidad Nacional Autónoma de México (IN235202). D.P.A and R.S.S.V. are recipients of scholarships from CONACyT and DGAPA-UNAM.
PY - 2005/8
Y1 - 2005/8
N2 - In human cells, biotin is essential to maintain metabolic homeostasis and as regulator of gene expression. The enzyme holocarboxylase synthetase (HCS) transforms biotin into its active form 5′-biotinyl-AMP and this compound is used to biotinylate five biotin-dependent carboxylases or to activate a soluble guanylate cyclase (sGC) and a cGMP-dependent protein kinase (PKG). The HCS-sGC-PKG pathway is responsible for maintaining the mRNA levels of enzymes involved in biotin utilization including HCS, carboxylases, and a biotin carrier known as sodium-dependent multivitamin transporter (SMVT). To understand the role of SMVT in the control of biotin utilization, we have studied the effect of biotin availability on SMVT protein and mRNA expression levels in HepG2 cells by Western blot analysis and rtPCR, respectively; and their functional impact on the rate of [3H]biotin uptake in human cells. Our results showed that human HepG2 cells grown in a biotin-deficient medium have a lower rate of biotin uptake than normal cells. The impairment in biotin uptake is associated with a reduction in the amount of both SMVT protein mass and mRNA levels. Transfection of HepG2 cells with a vector containing a luciferase reporter gene under the control of the rat SMVT promoter demonstrated that its transcriptional activity is regulated by biotin availability through activation of the HCS-sGC-PKG pathway. Our results support the proposed role of SMVT in the altruistic regulation of biotin utilization in liver cells that has been associated with sparing biotin depletion of the brain.
AB - In human cells, biotin is essential to maintain metabolic homeostasis and as regulator of gene expression. The enzyme holocarboxylase synthetase (HCS) transforms biotin into its active form 5′-biotinyl-AMP and this compound is used to biotinylate five biotin-dependent carboxylases or to activate a soluble guanylate cyclase (sGC) and a cGMP-dependent protein kinase (PKG). The HCS-sGC-PKG pathway is responsible for maintaining the mRNA levels of enzymes involved in biotin utilization including HCS, carboxylases, and a biotin carrier known as sodium-dependent multivitamin transporter (SMVT). To understand the role of SMVT in the control of biotin utilization, we have studied the effect of biotin availability on SMVT protein and mRNA expression levels in HepG2 cells by Western blot analysis and rtPCR, respectively; and their functional impact on the rate of [3H]biotin uptake in human cells. Our results showed that human HepG2 cells grown in a biotin-deficient medium have a lower rate of biotin uptake than normal cells. The impairment in biotin uptake is associated with a reduction in the amount of both SMVT protein mass and mRNA levels. Transfection of HepG2 cells with a vector containing a luciferase reporter gene under the control of the rat SMVT promoter demonstrated that its transcriptional activity is regulated by biotin availability through activation of the HCS-sGC-PKG pathway. Our results support the proposed role of SMVT in the altruistic regulation of biotin utilization in liver cells that has been associated with sparing biotin depletion of the brain.
KW - Altruistic metabolism
KW - Biotin utilization
KW - Biotin-dependent carboxylases
KW - Gene expression
KW - HCS
KW - Holocarboxylase synthetase
KW - Metabolic regulation
KW - SMVT
KW - Sodium-dependent multivitamin transporter
KW - Vitamin uptake
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U2 - 10.1016/j.ymgme.2005.04.001
DO - 10.1016/j.ymgme.2005.04.001
M3 - Article
C2 - 15905112
AN - SCOPUS:23044446759
SN - 1096-7192
VL - 85
SP - 301
EP - 307
JO - Molecular Genetics and Metabolism
JF - Molecular Genetics and Metabolism
IS - 4
ER -